1. Field of the Invention
This invention relates to aerofoil structures which are in the form of hollow containers or envelopes made of flexible material and which are ram air inflatable.
In particular, the invention is concerned with such structures when utilized for controlled operation such as in tethered flight. For example, when used as a kite or as a prime mover for land or water going craft.
The particular form of kite for which the structure of the invention is concerned is suitable for performing aerobatics or the like controlled flight by means of control lines connected with the structure.
2. Summaries of the Invention
According to a first aspect of the invention there is provided an air inflatable aerofoil structure, including a container or envelope formed of a flexible material and which is intended to be inflated by ram air, and means connectable with an edge zone of the container or envelope for maintaining the container or envelope in an extended position in which it can inflate under the action of ram air, and for providing anchorage for tethering lines, control lines, load carrying lines or support means, the arrangement being such that the container or envelope is downstream of said means.
According to a second aspect of the invention there is provided a ram air inflatable wing structure including an elongate container or envelope so formed as to have an aerofoil section when inflated by air, and elongated stiffening means so connectable with the container or envelope as to extend lengthwise of the leading edge zone thereof thereby to maintain the container or envelope in an extended condition in which it is inflatable and to provide, at each end thereof, an anchorage for one of a pair of control lines by which the flight of the structure can be controlled.
Preferably the stiffening means is such that the wing structure automatically adjusts its flight attitude in response to wind pressures acting thereupon.
According to a still further aspect of the invention there is provided a kite or other flyable structure including a ram air inflatable wing-like envelope having an aerofoil cross-section, and a flexible member connectable with the envelope such as to extend the full width of the leading edge, said member serving to hold the envelope in a spread out condition in which it can be inflated by ram air, to provide at the ends thereof anchorage points for two control lines by which the kite or other structure can be controlled in flight, and to permit the kite or other structure automatically to adjust its flight attitude according to the wind conditions.
Preferably, the adjustment of the flight attitude includes not only variation in the angle of attack of the aerofoil with respect to the wind forces but also variation in the shape of the envelope in a direction lengthwise thereof.
Preferably the stiffening means comprises an elongate flexible spar having characteristics of flexure or deformation from an initial shape such that it remains in its initial shape for wind pressures associated with relatively low wind velocities and such that it progressively deforms to accommodate the wind pressures acting on the envelope at higher wind velocities.
Conveniently, the container or envelope is provided with a sleeve or other means for receiving the stiffening means in a readily removeable manner.
The stiffening means can comprises a spar of glass or carbon fibre so as to be capable of deformation without permanent set.
Preferably the spar is hollow.
Preferably, ram air inlet means is provided along the whole length of the leading edge of the envelope.
It is also preferred to form the container or envelope as a multi-cell construction, with the walls of the cells running from the leading to trailing edge of the container or envelope.